I am a former EUROCONTROL software analyst-programmer in Flight Plan Processing at Karlsruhe UIR control center Karlsruhe with operational responsibility of maintenance and enhancement 1992 - 1997. My experience is in large systems also outside the ATC area. Systems psychology and human computer interaction areas are of special interest to me and I have taught in these areas at Istanbul Yeditepe University computer department.

Sunday, June 09, 2013

Bilincin hücresel zemini

An outline of:

The neuronal
basis for consciousness

R. Llina's, U. Ribary, D.
Contreras and C. Pedroarena

Department of Physiology and
Neuroscience, NewYork University School of Medicine, 550 First Avenue, NewYork,
NY 10016, USA

the interaction
between the specific and non-specificthalamic loops suggests that rather than a
gate into the brain, the thalamus represents a hub from which any site in the
cortex can communicate with any other such site or sites.

Indeed, this view followed the Jamesian postulate of
reflex (James 1890), in which the nervous system is organized as a set of
complex neuronal connectivity pathways triggered into action by the outside
world.

Bu görüşe
göre davranış esasen, algısal girişlerin sonucudur.

On this view,
behaviour is fundamentally the resultant of sensory input.

This general postulate contrasted with the point of view
espoused by Graham Brown (1914, 1915) and more recently by Nicholas Bernstein
(1967), who viewed spinal cord function as mostly organized as intrinsically
generated neuronal activity.With this
view sensory inputs are mostly modifiers of such intrinsic activity.

Likewise, in cognitive physiology the prevailing view today
is that consciousness is mostly the resultant of sensory input brought into the
brain by the different sensory afferents, the activity of which represent the functional
basis for cognition.

Indeed, the difference
must be functional. ...The questions would then be: (i) what is the fundamental
difference between being awake and being asleep?and (ii) what does it tell us about brain
function? ...

that the corticothalamic pathway can selectively enhance
coherence and synchron icity of activity between selected groups of
interconnected cortical and thalamic neurons during particular functional
states...

The state of responsiveness of thalamic neurons can be modulated by
changes in the membrane potential induced by neuromodulatory inputs originating
from the brainstem or the forebrain, but also by other central or peripheral
synaptic inputs.

In contrast, during activated states, such as waking or REM
sleep, high-frequency oscillations (20^50Hz) show a pattern of coherence that
is either restricted to its immediate vicinity (Steriade et al. 1996a) or occurs
between distant discrete areas (Ribary et al. 1991).

cortical inhibitory
neurons are capable of high-frequency oscilla tion (Llina¨ s et al. 1991) and with
the view that, if such neurons are synaptically coupled and fire in synchrony,
they might be formative in generating cortical gamma-band activity.

a central difference remains: that of the inability of
sensory input to reset the 40Hz activity during REM sleep. In contrast, during
slow-wave sleep the amplitude of these oscillators differs from that of
wakefulness and REM sleep but, as in REM sleep, there is no 40Hz sensory
response.

Anothersignificant finding is that gamma oscillations
are not reset by sensory input during REM sleep, although clear evoked-potential
responses indicate that the thalamo- neocortical system is accessible to
sensory input.We consider this to be
the central difference between dreaming and wakefulness.

These results suggest
that we do not perceive the external world during REM sleep because the
intrinsic activity of the nervous system does not place sensory input in the
context of the functional state being generated by the brain (Llina¨ s &
Pare¨ 1991).

An attractive possibility in considering the morpho- physiological
substrate is that the `non-specific' thalamic system, particularly the
intralaminar complex, has an important role in such coincidence generation.

This possibility is particularly attractive given that (i)
single neurons burst at 30^40Hz (Steriade et al. 1993a), especially
during REM sleep, a finding that is consistent with the macroscopic magnetic
recordings observed in this study; and (ii) damage of the intralaminar system
results in lethargy or coma (Fac°on et al. 1958; Castaigne et al. 1962).

...

Sonuç
olarak, sistem zamansal uyum zemininde işler.

In conclusion, the system
would function on the basis of temporal coherence.

In this fashion the
time-coherent activity of the specific and non-specific oscillatory inputs, by
summing distal and proximal activity in given dendritic elements, would enhance
de facto 40Hz cortical coherence
by their multimodal character and in this way would provide one mechanism for global
binding.

The `specific' system
would thus provide the content that relates to the external world, and the non-specific
system would give rise to the temporal conjunction, or the context (on the
basis of a more interoceptive context concerned with alertness), that would together
generate a single cognitive experience.